Yes. Some visitors to your site have a virus. That virus picked up your email address from the page and now they'll be sending you those emails until their computers are virus free (or off-line). There's not much you can do about those who already sent you these emails since all the email addresses within it are likely forged (or at least not that of the actual sender).
You can try something like this:
http://www.tgpkit.com/htmlencode.php
I'm not sure how long this will last before virus coders start looking for that too (if they haven't already started) but I still see a LOT of "plaintext" email address out there for harvest... so perhaps they'll be happy with the current methods for a little while yet and leave the encoded ones alone.
And yes, I still get these emails from the early days of email worms (back to Sircam.A) by people withut a [real] return email address. The newer worms still seem to be thwarted by the encoded email address, but if you're in the address book of your customers/visitors, your email may still get plucked out for sending to on occasion (unfortunately, even that can add up).
A filter at the email server level is probably the best route to go if things get really out of hand.
HTH